This application claims the priority of Austrian Patent Application Serial No. GM 434/2000, filed Jun. 9, 2000.
The present invention relates, in general, to a track maintenance machine, and more particularly to a mobile tamping machine for tamping ballast under a railroad track.
U.S. Pat. No. 4,905,604 describes a tamping machine for tamping straight and switch sections of a railroad track. The tamping machine includes a machine frame which is supported on undercarriages for travel on a main track in an operating direction. A tamping unit is mounted on the machine frame between the undercarriages, and a track lifting and lining unit is vertically and transversely adjustably mounted on the machine frame immediately ahead of the tamping unit in the operating direction for leveling and lining the main track. In addition, the tamping machine includes an auxiliary lifting unit which is mounted on the machine frame for lifting a branch track branching off the main track at a track switch. A special measuring system is provided to control the lifting of the branch track by the auxiliary lifting unit, and includes a measuring axle running on the main track and another measuring axle running on the branch track. The two measuring axles are coupled together by a rod carrying a cross level indicator. In this manner, an operator is able to lift the branch track by remote-controlled operation of the auxiliary lifting unit to accurately conform a lifting of the branch track to a lifting of the main track by closely monitoring the cross level indicator.
It would be desirable and advantageous to provide an improved tamping machine which is simple in structure and yet ensures an exact conformity between the vertical positions of the main and branch tracks at a switch.
According to one aspect of the present invention, a tamping machine includes a machine frame supported on undercarriages for travel on a main track in an operating direction; a tamping unit mounted on the machine frame between the undercarriages; a track lifting and lining unit, vertically and transversely adjustably mounted on the machine frame immediately ahead of the tamping unit in the operating direction, for leveling and lining the main track; drive means for vertically and transversely adjusting the track lifting and lining unit; an auxiliary lifting unit, mounted on the machine frame, for lifting a branch track branching off the main track at a track switch; and a measuring system, operatively connected to both the track lifting and lining unit and the auxiliary lifting unit, for controlling a lifting of the track switch, wherein the measuring system includes a mechanical measuring device, which connects the track lifting and lining unit to the auxiliary lifting device and is telescopically extendible in a direction transversely to the longitudinal axis of the machine frame, and a measuring sensor.
Such a common measuring system has a simple configuration and is yet able to realize an automatic and accurate coordination of both the track lifting and lining unit and the auxiliary lifting unit. In this way, an accurate and swift track position correction can be accomplished without any problems, even when track switches are involved which have long ties with an elastic joint. As a consequence of the simplicity of the measuring system, the correction of the track position is not impaired in any way and the operator""s view of the track remains unobstructed.
According to another feature of the present invention, the mechanical measuring device may be a cable and the measuring sensor may be a rotary potentiometer operatively connected to the cable. Another option may include the configuration of the measuring device as a measuring beam and the configuration of the measuring sensor as a goniometer operatively connected to the measuring beam. Suitably, the measuring beam is configured so as to be telescopically extendible.
According to another feature of the present invention, the tamping machine may further include a lifting drive, connected to the auxiliary lifting unit, for lifting the branch track, and a control device, connected to the measuring sensor, for actuating the lifting drive.